1. Field of the Invention
The present invention belongs to the field of technology of a light-emitting apparatus including a light-emitting device and a production method thereof.
2. Description of the Related Art
An organic electroluminescent device utilizing electroluminescence (hereinafter, simply referred to as EL) of an organic material has attracted attention as a light-emitting device which can emit light at a high luminance by low-voltage driving.
A display apparatus of an active matrix type using such an organic EL device (i.e., organic EL display) is provided with a thin film transistor (hereinafter, simply referred to as TFT) in each of pixels formed on a substrate. The organic EL device is formed on an interlayer insulating film formed so as to cover the TFTs.
The organic EL device has a first electrode patterned for each of the pixels in a state of being connected to the TFTs and an insulating device isolation layer which exposes the central portion of the first electrode as a pixel opening and cover the peripheral portion thereof. The device is configured to further include an organic layer provided on the first electrode in the pixel opening isolated by the device isolation layer, and a second electrode provided in a state of covering the organic layer. Of the electrodes, the second electrode is usually formed so as to cover a plurality of pixels, and is used commonly for the plurality of pixels.
In the organic EL device configured as described above, organic layers corresponding to each color are formed in the same stack structure within the pixel opening surrounded by the device isolation layer by use of several kinds of shadow masks, so that high mask alignment accuracy is required. In general, when an organic layer is formed by vapor deposition with a shadow mask, several kinds of shadow masks are pressed against to the device isolation layer, organic layers are formed into a stack film.
Further, in such an active matrix type display apparatus, in order to secure a pixel aperture ratio of the organic EL device, it is effective to adopt the so-called top emission structure in which light is extracted from the side opposite to the substrate. Hence, the second electrode is required to be small in thickness to secure light transmittance, whereby the resistance value increases to makes it easy to cause a voltage drop.
Hence, a configuration is proposed, in which an auxiliary electrode made of a metal material with good conductivity is formed, and the auxiliary electrode is connected to a second electrode, thereby preventing the voltage drop of the second electrode. In Japanese Patent Application Laid-Open No. 2002-318556, there is proposed a configuration in which an auxiliary electrode is formed in the same layer as a first electrode, an organic layer is then formed on the first electrode, after which a second electrode is formed, and the auxiliary electrode is then connected to the second electrode. Further, in Japanese Patent Application Laid-Open No. 2003-316291, a configuration is proposed in which an auxiliary electrode is formed on a bank, an organic light-emitting medium is then formed, and thereafter a second electrode is formed, and the auxiliary electrode is then connected to the second electrode.
As described above, when the organic layer is formed by vapor deposition using the shadow mask, organic layers are formed into a stack film with several kinds of the shadow masks being pressed against the device isolation layer. However, there has been a problem that at that time, the thus formed organic layers are damaged by the shadow masks to reduce the production yield.
However, although the display apparatus and the production method thereof as proposed in Japanese Patent Application Laid-Open No. 2002-318556 are configured to be capable of preventing the voltage drop of the second electrode, the above described problem is not yet solved.
Further, in the light-emitting apparatus and the production method as proposed in Japanese Patent Application Laid-Open No. 2003-316291, since the film deposition of the organic light-emitting medium is performed without bringing the mask into contact the substrate side, there are problems such that the film thickness of each pixel varies and a shift of the alignment is produced due to the bending of the mask. Further, there are also the problems that a film of the organic light-emitting medium is deposited on the auxiliary electrode to interrupt the electrical conduction between the auxiliary electrode and the second electrode, or the resistance value increases due to the organic light-emitting medium, so that the function as the auxiliary electrode cannot sufficiently be exhibited.